There are various systems for superposing and displaying subtitles on a video, and Timed Text Markup Language (TTML) as subtitle data in the Extensible Markup Language (XML) form, which enables a display region, a display timing and the like to be controlled, are increasingly used.
TTML can be associated with a web application such as HTML5, and has a property that it can use not only character codes but also bit maps.
Note that, TTML is described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-169885), for example.